Assigning shared catalogs to cache structures in a cluster computing system

ABSTRACT

An apparatus, system, and method for assigning a cache structure to a catalog. The apparatus includes an identification module configured to identify a catalog for sharing in association with a coupling facility. The coupling facility includes a plurality of cache structures for catalogs of a cluster computing system. The coupling facility is configured to facilitate data sharing among a plurality of host systems of the cluster computing system. The apparatus includes a selection module configured to select a cache structure of the plurality of cache structures for the catalog based on one or more usage status indicators according to an assignment policy. The apparatus includes a storage module configured to store catalog information of the catalog in the cache structure in response to the selection module selecting the cache structure.

BACKGROUND

1. Field

The subject matter disclosed herein relates to shared catalogs and moreparticularly relates to assigning shared catalogs to cache structures.

2. Description of the Related Art

Cluster computing systems, such as IBM® Corporation's Parallel Sysplex,allow for parallel computing, data recovery, and the like. A typicalcluster includes multiple host systems linked together to enable dataand workload sharing, acting as a single system. In a Sysplex, aCoupling Facility is typically used to coordinate and manage datasharing and access.

Often these cluster computing systems use catalogs that includeinformation, such as location information, about the data sets residingon storage of the system. These catalogs are typically shared among hostsystems of the cluster. Using Enhanced Catalog Sharing (ECS), thecoupling facility may store update information for catalogs, allowinghost systems to access the update information from the coupling facilityinstead of from storage.

BRIEF SUMMARY

An apparatus is presented. In one embodiment, the apparatus includes anidentification module configured to identify a catalog for sharing inassociation with a coupling facility. The coupling facility may includea plurality of cache structures for catalogs of a cluster computingsystem. The coupling facility may be configured to facilitate datasharing among a plurality of host systems of the cluster computingsystem. In one embodiment, the apparatus includes a selection moduleconfigured to select a cache structure of the plurality of cachestructures for the catalog based on one or more usage status indicatorsaccording to an assignment policy. In one embodiment, the apparatusincludes a storage module configured to store catalog information of thecatalog in the cache structure in response to the selection moduleselecting the cache structure.

A method for assigning a cache structure to a catalog is presented. Inone embodiment, the method includes identifying a catalog for sharing inassociation with a coupling facility. The coupling facility may includea plurality of cache structures for catalogs of a cluster computingsystem. The coupling facility may be configured to facilitate datasharing among a plurality of host systems of the cluster computingsystem. In one embodiment, the method includes assigning the catalog toa cache structure of the plurality of cache structures based on one ormore usage status indicators according to an assignment policy. In oneembodiment, the method includes storing catalog information of thecatalog in the cache structure in response to selecting the cachestructure.

A computer program product comprising a computer readable storage mediumstoring machine readable code executed by a processor to performoperations for assigning a cache structure to a catalog is presented. Inone embodiment, the operations include identifying a catalog for sharingin association with a coupling facility according to Enhanced CatalogSharing (ECS). The coupling facility may include a plurality of cachestructures for catalogs of a cluster computing system. The couplingfacility may be configured to facilitate data sharing among a pluralityof host systems of the cluster computing system. In one embodiment, theoperations include assigning the catalog to a cache structure of theplurality of cache structures based on one or more of an availabilityindicator and catalog usage according to an assignment policy stored ina coupling facility resource management (CFRM) data set of the clustercomputing system. In one embodiment, the operations include storing aVirtual Storage Access Method (VSAM) volume record (VVR) correspondingto the catalog in the cache structure in response to selecting the cachestructure. The VVR may include update information.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the embodiments of the invention will bereadily understood, a more particular description of the embodimentsbriefly described above will be rendered by reference to specificembodiments that are illustrated in the appended drawings. Understandingthat these drawings depict only some embodiments and are not thereforeto be considered to be limiting of scope, the embodiments will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings, in which:

FIG. 1 is a schematic block diagram illustrating one embodiment of asystem for assigning shared catalogs to cache structures in accordancewith the present subject matter;

FIG. 2 is a schematic block diagram illustrating another embodiment of asystem for assigning shared catalogs to cache structures in accordancewith the present subject matter;

FIG. 3A is a schematic block diagram illustrating one embodiment of acoupling facility cache in accordance with the present subject matter;

FIG. 3B is a schematic block diagram illustrating one embodiment ofisolating a catalog volume record in accordance with the present subjectmatter;

FIG. 4A is a schematic block diagram illustrating another embodiment ofa coupling facility cache in accordance with the present subject matter;

FIG. 4B is a schematic block diagram illustrating one embodiment ofmoving a catalog volume record in accordance with the present subjectmatter;

FIG. 5 is a schematic block diagram illustrating one embodiment of anassignment apparatus;

FIG. 6 is a schematic block diagram illustrating another embodiment ofan assignment apparatus;

FIG. 7 is a schematic flow chart diagram illustrating one embodiment ofa method for assigning shared catalogs to cache structures; and

FIG. 8 is a schematic flow chart diagram illustrating another embodimentof method for assigning shared catalogs to cache structures.

DETAILED DESCRIPTION

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. Thus, appearances of the phrases“in one embodiment,” “in an embodiment,” and similar language throughoutthis specification may, but do not necessarily, all refer to the sameembodiment, but mean “one or more but not all embodiments” unlessexpressly specified otherwise. The terms “including,” “comprising,”“having,” and variations thereof mean “including but not limited to”unless expressly specified otherwise. An enumerated listing of itemsdoes not imply that any or all of the items are mutually exclusiveand/or mutually inclusive, unless expressly specified otherwise. Theterms “a,” “an,” and “the” also refer to “one or more” unless expresslyspecified otherwise.

Furthermore, the described features, advantages, and characteristics ofthe embodiments may be combined in any suitable manner. One skilled inthe relevant art will recognize that the embodiments may be practicedwithout one or more of the specific features or advantages of aparticular embodiment. In other instances, additional features andadvantages may be recognized in certain embodiments that may not bepresent in all embodiments.

These features and advantages of the embodiments will become more fullyapparent from the following description and appended claims, or may belearned by the practice of embodiments as set forth hereinafter. As willbe appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method, and/or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module,” or“system.”Furthermore, aspects of the present invention may take the formof a computer program product embodied in one or more computer readablemedium(s) having program code embodied thereon.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom VLSI circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of program code may, forinstance, comprise one or more physical or logical blocks of computerinstructions which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of program code may be a single instruction, or manyinstructions, and may even be distributed over several different codesegments, among different programs, and across several memory devices.Similarly, operational data may be identified and illustrated hereinwithin modules, and may be embodied in any suitable form and organizedwithin any suitable type of data structure. The operational data may becollected as a single data set, or may be distributed over differentlocations including over different storage devices, and may exist, atleast partially, merely as electronic signals on a system or network.Where a module or portions of a module are implemented in software, theprogram code may be stored and/or propagated on in one or more computerreadable medium(s).

The computer readable medium may be a tangible computer readable storagemedium storing the program code. The computer readable storage mediummay be, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, infrared, holographic, micromechanical, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing.

More specific examples of the computer readable storage medium mayinclude but are not limited to a portable computer diskette, a harddisk, a random access memory (RAM), a read-only memory (ROM), anerasable programmable read-only memory (EPROM or Flash memory), aportable compact disc read-only memory (CD-ROM), a digital versatiledisc (DVD), an optical storage device, a magnetic storage device, aholographic storage medium, a micromechanical storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain, and/or store program code for use by and/or in connection withan instruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signalmedium. A computer readable signal medium may include a propagated datasignal with program code embodied therein, for example, in baseband oras part of a carrier wave. Such a propagated signal may take any of avariety of forms, including, but not limited to, electrical,electro-magnetic, magnetic, optical, or any suitable combinationthereof. A computer readable signal medium may be any computer readablemedium that is not a computer readable storage medium and that cancommunicate, propagate, or transport program code for use by or inconnection with an instruction execution system, apparatus, or device.Program code embodied on a computer readable signal medium may betransmitted using any appropriate medium, including but not limited towire-line, optical fiber, Radio Frequency (RF), or the like, or anysuitable combination of the foregoing

In one embodiment, the computer readable medium may comprise acombination of one or more computer readable storage mediums and one ormore computer readable signal mediums. For example, program code may beboth propagated as an electro-magnetic signal through a fiber opticcable for execution by a processor and stored on RAM storage device forexecution by the processor.

Program code for carrying out operations for aspects of the presentinvention may be written in any combination of one or more programminglanguages, including an object oriented programming language such asJava, Smalltalk, C++, PHP or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

The computer program product may be shared, simultaneously servingmultiple customers in a flexible, automated fashion. The computerprogram product may be standardized, requiring little customization andscalable, providing capacity on demand in a pay-as-you-go model.

The computer program product may be stored on a shared file systemaccessible from one or more servers. The computer program product may beexecuted via transactions that contain data and server processingrequests that use Central Processor Unit (CPU) units on the accessedserver. CPU units may be units of time such as minutes, seconds, hourson the central processor of the server. Additionally the accessed servermay make requests of other servers that require CPU units. CPU units arean example that represents but one measurement of use. Othermeasurements of use include but are not limited to network bandwidth,memory usage, storage usage, packet transfers, complete transactionsetc.

When multiple customers use the same computer program product via sharedexecution, transactions are differentiated by the parameters included inthe transactions that identify the unique customer and the type ofservice for that customer. All of the CPU units and other measurementsof use that are used for the services for each customer are recorded.When the number of transactions to any one server reaches a number thatbegins to affect the performance of that server, other servers areaccessed to increase the capacity and to share the workload. Likewisewhen other measurements of use such as network bandwidth, memory usage,storage usage, etc. approach a capacity so as to affect performance,additional network bandwidth, memory usage, storage etc. are added toshare the workload.

The measurements of use used for each service and customer are sent to acollecting server that sums the measurements of use for each customerfor each service that was processed anywhere in the network of serversthat provide the shared execution of the computer program product. Thesummed measurements of use units are periodically multiplied by unitcosts and the resulting total computer program product service costs arealternatively sent to the customer and or indicated on a web siteaccessed by the customer which then remits payment to the serviceprovider.

In one embodiment, the service provider requests payment directly from acustomer account at a banking or financial institution. In anotherembodiment, if the service provider is also a customer of the customerthat uses the computer program product, the payment owed to the serviceprovider is reconciled to the payment owed by the service provider tominimize the transfer of payments.

The computer program product may be integrated into a client, server andnetwork environment by providing for the computer program product tocoexist with applications, operating systems and network operatingsystems software and then installing the computer program product on theclients and servers in the environment where the computer programproduct will function.

In one embodiment software is identified on the clients and serversincluding the network operating system where the computer programproduct will be deployed that are required by the computer programproduct or that work in conjunction with the computer program product.This includes the network operating system that is software thatenhances a basic operating system by adding networking features.

In one embodiment, software applications and version numbers areidentified and compared to the list of software applications and versionnumbers that have been tested to work with the computer program product.Those software applications that are missing or that do not match thecorrect version will be upgraded with the correct version numbers.Program instructions that pass parameters from the computer programproduct to the software applications will be checked to ensure theparameter lists match the parameter lists required by the computerprogram product. Conversely parameters passed by the softwareapplications to the computer program product will be checked to ensurethe parameters match the parameters required by the computer programproduct. The client and server operating systems including the networkoperating systems will be identified and compared to the list ofoperating systems, version numbers and network software that have beentested to work with the computer program product. Those operatingsystems, version numbers and network software that do not match the listof tested operating systems and version numbers will be upgraded on theclients and servers to the required level.

In response to determining that the software where the computer programproduct is to be deployed, is at the correct version level that has beentested to work with the computer program product, the integration iscompleted by installing the computer program product on the clients andservers.

Furthermore, the described features, structures, or characteristics ofthe embodiments may be combined in any suitable manner. In the followingdescription, numerous specific details are provided, such as examples ofprogramming, software modules, user selections, network transactions,database queries, database structures, hardware modules, hardwarecircuits, hardware chips, etc., to provide a thorough understanding ofembodiments. One skilled in the relevant art will recognize, however,that embodiments may be practiced without one or more of the specificdetails, or with other methods, components, materials, and so forth. Inother instances, well-known structures, materials, or operations are notshown or described in detail to avoid obscuring aspects of anembodiment.

Aspects of the embodiments are described below with reference toschematic flowchart diagrams and/or schematic block diagrams of methods,apparatuses, systems, and computer program products according toembodiments of the invention. It will be understood that each block ofthe schematic flowchart diagrams and/or schematic block diagrams, andcombinations of blocks in the schematic flowchart diagrams and/orschematic block diagrams, can be implemented by program code. Theprogram code may be provided to a processor of a general purposecomputer, special purpose computer, sequencer, or other programmabledata processing apparatus to produce a machine, such that theinstructions, which execute via the processor of the computer or otherprogrammable data processing apparatus, create means for implementingthe functions/acts specified in the schematic flowchart diagrams and/orschematic block diagrams block or blocks.

The program code may also be stored in a computer readable medium thatcan direct a computer, other programmable data processing apparatus, orother devices to function in a particular manner, such that theinstructions stored in the computer readable medium produce an articleof manufacture including instructions which implement the function/actspecified in the schematic flowchart diagrams and/or schematic blockdiagrams block or blocks.

The program code may also be loaded onto a computer, other programmabledata processing apparatus, or other devices to cause a series ofoperational steps to be performed on the computer, other programmableapparatus or other devices to produce a computer implemented processsuch that the program code which executed on the computer or otherprogrammable apparatus provide processes for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The schematic flowchart diagrams and/or schematic block diagrams in theFigures illustrate the architecture, functionality, and operation ofpossible implementations of apparatuses, systems, methods and computerprogram products according to various embodiments of the presentinvention. In this regard, each block in the schematic flowchartdiagrams and/or schematic block diagrams may represent a module,segment, or portion of code, which comprises one or more executableinstructions of the program code for implementing the specified logicalfunction(s).

It should also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order noted in theFigures. For example, two blocks shown in succession may, in fact, beexecuted substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. Other steps and methods may be conceived that are equivalentin function, logic, or effect to one or more blocks, or portionsthereof, of the illustrated Figures.

Although various arrow types and line types may be employed in theflowchart and/or block diagrams, they are understood not to limit thescope of the corresponding embodiments. Indeed, some arrows or otherconnectors may be used to indicate only the logical flow of the depictedembodiment. For instance, an arrow may indicate a waiting or monitoringperiod of unspecified duration between enumerated steps of the depictedembodiment. It will also be noted that each block of the block diagramsand/or N flowchart diagrams, and combinations of blocks in the blockdiagrams and/or flowchart diagrams, can be implemented by specialpurpose hardware-based systems that perform the specified functions oracts, or combinations of special purpose hardware and program code.

The description of elements in each figure may refer to elements ofproceeding figures. Like numbers refer to like elements in all figures,including alternate embodiments of like elements.

FIG. 1 is a schematic block diagram illustrating one embodiment of asystem 100 for assigning shared catalogs to cache structures inaccordance with the present subject matter. Specifically, FIG. 1 depictsa cluster computing system 100. In one embodiment, the cluster computingsystem 100 is a Parallel Sysplex, such as the S/390, from InternationalBusiness Machines Corporation, Armonk, N.Y., or other suitable clustercomputing system. The system 100 includes a plurality of host systems110. Each host system 110 may include one or more processors, memory,and the like. The processors 105 executes the computer readable programsas known to those skilled in the art. Each host system 110 may beembodied as a mainframe computer. In one embodiment, each host system110 includes a Z/OS® operating system by International Business MachinesCorporation of Armonk, N.Y. Each host system 110 may provide one or moreLogical Partitions (LPARs). Specifically, an LPAR is a type of virtualmachine comprising a virtualization of the host system's 110 resources.A host system 110 may be partitioned into multiple LPARs and each LPARmay host a separate instance of the operating system. Although threehost systems 110 are depicted, the cluster computing system 100 mayinclude any suitable number of host systems 110. The memory storescomputer readable programs.

The plurality of host systems 110 communicate with a plurality of directaccess storage device (DASDs) 120 shared among the host systems 110. TheDASDs 120 may comprise secondary storage devices, disk arrays, and thelike. The host systems 110 read data from the DASDs 120. Specifically,the DASDs 120 may store data sets for access by the host systems 110.Although four DASDs 120 are depicted, the system may include anysuitable number of DASDs 120.

The host systems 110 may access data from the DASDs 120 according to avirtual storage access method (VSAM). The host systems 110 may connectto the DASDs 120 through a switch 115, such as a fibre connection(FICON) switch. Furthermore, an external time source (not depicted) orServer Time Protocol (STP) implemented by the host systems 110 may beused to synchronize the clocks of the host systems 110.

Catalogs may be used to facilitate locating data sets and to categorizedata in the cluster computing system 100. A catalog is itself a data setthat includes information about other data sets. Each VSAM data set iscataloged. Catalogs may be master catalogs or user catalogs. Each hostsystem 110 has a master catalog with entries for system data sets. Usercatalogs include entries for application specific data sets.

Catalogs may be shared among host systems 110 and an integrated catalogfacility (ICF) structure may be used by the system for catalog sharing.Catalogs may have two parts: the basic catalog structure (BCS) and theVSAM volume data set (VVDS). The VVDS may include catalog updateinformation so that host systems 110 may detect changes made tocatalogs. This catalog update information may be referred to as a volumerecord generally and a VSAM volume record (VVR) or integrity VVRspecifically. A host system 110 that modifies the catalog may store arecord of the change (e.g. a timestamp and counter update) and may checkthe VVR to ensure that it has the latest version of data stored incache. Instead of reading the VVR stored on disk, catalogs may be sharedaccording to Enhanced Catalog Sharing (ECS), which involves storing theVVR on a coupling facility 105 to reduce I/O to a catalog data set ondisk as described below.

The host systems 110 communicate with a coupling facility 105. Thecoupling facility 105 coordinates data access and synchronization by thehost systems 110. The coupling facility 105 may be separately embodiedfrom the host systems 110 as depicted. For example, the couplingfacility 105 may be embodied as a separate mainframe unit. In certainembodiments, the coupling facility 105 may execute in an LPAR.

The coupling facility 105 may execute in an LPAR on a mainframe externalfrom the host systems 110. In one embodiment, the coupling facility 105executes in an LPAR on a host system 110. The LPAR may be specialized toexecute coupling facility code. The coupling facility 105 maycommunicate with host systems 110 (e.g. LPARs on host systems 110)through coupling facility channels. In certain embodiments, one or moreof the host systems 110 include a console (not depicted) incommunication with the host system 110. The console may be a computingdevice that allows a user to enter commands, such as through a keyboardand mouse, and to view output, such as through a display device.

The coupling facility 105 includes a processor, memory, and aspecialized operating system referred to as Coupling Facility ControlCode (CFCC). The coupling facility 105 may provide locking and cachingfor shared data among the host systems 110. Although a single couplingfacility 105 is depicted, in certain embodiments, the system 100 mayinclude multiple coupling facilities.

The coupling facility 105 may be configured by a coupling facilityresource management (CFRM), a specialized data set which specifiesbehavior and other specifications of the coupling facility 105. Inaddition, the coupling facility 105 may provide dedicated portions ofmemory called structures for reference by the host systems 110. A cachestructure is one such structure.

The coupling facility 105 may provide cache structures for ECS catalogsharing (hereinafter “ECS cache structures”). As described above,catalogs may be shared according to ECS to reduce I/O to a catalog dataset on disk as described below. As part of ECS, the coupling facility105 stores volume records in the ECS cache structure. As a result, hostsystems 110 may be notified by the coupling facility 105 when changes tocatalogs have occurred and may update the volume record in the couplingfacility 105 without having to access the DASDs 120. Host systems 110typically disconnect from a catalog if it requires maintenance or if thecatalog is a master catalog for a host system 110 that will undergomaintenance. In cluster computing systems with a single cache structure,the host systems 110 disconnect each host system 110 from the cachestructure and hence, from the volume records for all catalogs in ECSeven if only a subset of the catalogs are affected. During thedisconnect, the host systems 110 typically fall back to referencing thevolume record from the DASDs 120.

In one embodiment, the coupling facility 105 provides a plurality of ECScache structures. Each ECS cache structure may store one or more volumerecords. In one embodiment, the host systems 110 may disconnect fromonly the cache structures with the affected catalogs. For example, if avolume record for a first catalog is stored in a first ECS cachestructure and a volume record for a second catalog is stored in a secondECS cache structure and the first catalog is scheduled for maintenance,the host systems 110 may disconnect from the first ECS cache structurewhile maintaining a connection to the second ECS cache structure.

FIG. 2 is a schematic block diagram illustrating another embodiment of asystem 200 for assigning shared catalogs to cache structures inaccordance with the present subject matter. The system 200 includes thecoupling facility 105 of FIG. 1 and exemplary host systems 110 andshared DASDs 120 similar to the like-named components of FIG. 1. In thedepicted embodiment, the shared DASDs 120 store catalogs 245.Specifically, a first DASD 120 stores Catalog A 245 and a second DASD120 stores Catalog B 245.

Each host system 110 includes a catalog module 225. In one embodiment,the catalog module 225 includes code, logic and functions to accesscatalogs 245 from the DASDs 120, read catalog data 235, 240 (e.g.catalog records) into cache, write catalog data 235, 240 to the DASDs120, and the like. In one embodiment, the catalog module 225 includesthe functionality of Catalog Address Space (CAS) which is devoted tocatalog processing. The catalog module 225 may maintain a local mapmapping catalogs 245 to their corresponding ECS cache structures 215 inthe coupling facility 105. A host system 110 may synchronize its localmap with a global map on the coupling facility 105 that has a mastermapping of catalogs to ECS cache structures.

The catalog module 225, in one embodiment, is a persistent process thatis started at host system 110 startup and that interacts with thecoupling facility 105 for ECS. The ECS functions of a host system 110may connect with the ECS cache structures 215 to access volume recordsfor the catalogs 245 of the system 200. The catalog module 225 mayexecute as part of an operating system of the host system 110.Furthermore, the operating system may execute within an LPAR.

The coupling facility 105 includes a processor 205 and a memory 206. Thememory 206 includes a cache 210 with a plurality of ECS cache structures215. While FIG. 2 depicts two ECS cache structures 215, the cache 210may include any suitable number of ECS cache structures 215 as describedbelow. The ECS cache structures 215 may store volume records for thecatalogs 245 accessed by the host systems 110. In one embodiment, whenthe catalog module 225 opens an ECS eligible catalog 245, the volumerecord is copied into the coupling facility 105 (e.g. to an ECS cachestructure 215). Furthermore, a global ECS map may be stored by thecoupling facility 105 to map each catalog 245 to an ECS cache structure245.

The existence of multiple ECS cache structures 215 allows for variationin storing volume records. Consequently, the system 200 includes anassignment apparatus 220. The assignment apparatus 220 manages theassignment of catalog volume records to ECS cache structures 215.Specifically, in certain embodiments, the assignment apparatus 220assigns ECS cache structures 215 to volume records based on usage statusindicators such as catalog usage statistics, availability schedules(e.g. when the catalog 245 or host system 110 for a catalog 245 will beoffline), error rates of a particular catalog 245, and the like. Theassignment apparatus 220 may assign volume records to cache structures215 based on an assignment policy having specifications, rules, and/orthresholds that specify when to move a volume record, where to assign avolume record, and the like. The movement of catalogs 245 between ECScache structures 215 may be done dynamically as performance andstatistical data changes, modifying cache structure assignmentsaccordingly.

Although FIG. 2 depicts the assignment apparatus 220 as executing in thecoupling facility 105, all or a portion of the assignment apparatus 220may execute in one or more host systems 110, one or more host systems110 and the coupling facility 105, or the like. For example, theassignment apparatus 220 may be part of the catalog module 225, the ECSfunctions, or the like, of one or more of the host systems 110. In oneembodiment, all or a portion of the assignment apparatus 220 is ascheduled batch process than executes on a periodic basis.

FIG. 3A is a schematic block diagram illustrating one embodiment of acoupling facility cache 210 in accordance with the present subjectmatter. The coupling facility cache 210 may be the cache 210 of FIG. 2.Specifically, the coupling facility cache 210 includes an ECS cachestructure 215 with a volume record 300 (e.g. a VVR) for Catalog A 245and a volume record 305 for Catalog B 245. As depicted in FIG. 3B, theassignment apparatus 220 may move a volume record from one ECS cachestructure 215 to another. In the depicted embodiment, the volume record305 for Catalog B 245 is moved 310 to cache structure B 215. In certainembodiments, Catalog B volume record 305 may be isolated in cachestructure B 215 such that no other volume records 305 are assigned andresiding in cache structure B 215. The assignment apparatus 220 mayisolate a particular volume record 305 for a particular catalog 245 inresponse to one or more of determining that the particular catalog 245is damaged (e.g. by detecting an amount of errors that meet athreshold), determining that a host system 110 corresponding to theparticular catalog 245 will be unavailable, and determining that theparticular catalog 245 will be unavailable such as, for example, beingscheduled for maintenance.

FIG. 4A is a schematic block diagram illustrating another embodiment ofa coupling facility cache 210 in accordance with the present subjectmatter. FIG. 4A includes on embodiment of the cache 210 of FIG. 2. Thecache 210 includes cache structure A 215 and cache structure B 215.Cache structure A 215 includes a volume record 400 for Catalog A 245 anda volume record 405 for Catalog B 245. Furthermore, cache structure B215 includes a volume record 410 for Catalog C. As depicted, theassignment apparatus 220 may retrieve catalog usage statistics oncatalogs 245 with corresponding volume records in cache. The catalogusage statistics may include a number of searches performed on thesecatalogs 245 indicating a level of access. In the depicted embodiment,Catalog A has had 16,546 searches, catalog B has had 15,089 searches,and Catalog C has had 10 searches.

As depicted in Figure B, the assignment apparatus 220 may move 415Catalog B 245 into cache structure B 215 so as to more thoroughlybalance I/O to the cache structures 215, as the number of searches onCatalog C 245 is not substantial. As a result, each cache structure 215may receive a more equal amount of I/O in the future.

FIG. 5 is a schematic block diagram illustrating one embodiment of anassignment apparatus 220. The assignment apparatus 220 may be oneembodiment of the assignment apparatus 220 of FIG. 2. The assignmentapparatus 220 includes an identification module 500, a selection module505, and a storage module 510.

The identification module 500, in one embodiment, identifies a catalog245 for assignment evaluation. The catalog 245 may be for sharing inassociation with a coupling facility 105. In a further embodiment, thecatalog 245 is for ECS sharing as described above. In one embodiment,the identification module 500 may identify a catalog 245 for initialassignment into an ECS cache structure 215. In this embodiment, theidentification module 500 may identify a catalog 245 for assignmentevaluation in response to a catalog module 225 opening the catalog 245where the volume record is prepared for copying into the couplingfacility 105.

In one embodiment, the identification module 500 identifies a catalog245 for assignment evaluation that is already active in the couplingfacility 105 and already has its (q volume record stored in an ECS cachestructure 215. For example, the identification module 500, as part of ascheduled batch process, may monitor various catalogs 245, iteratethrough catalogs 245 and evaluate each one for reassignment. Catalogs245 identified by the identification module 500 may be user catalogs ormaster catalogs. In one embodiment, the identification module 500identifies a particular catalog 245 in response to catalog usage of theparticular catalog 245 meeting a threshold. For example, catalogs 245used more heavily in comparison with other catalogs 245 may be isolatedas described above.

The selection module 505, in one embodiment, selects a cache structure215 of the plurality of cache structures 215 for the catalog 245 basedon one or more usage status indicators according to an assignmentpolicy. The selection module 505 may also assign a catalog 245 to acache structure 215 based on these usage status indicators. In oneembodiment, the usage status indicators include catalog usage statisticssuch as a number of searches for catalogs 245, performance data, and thelike. The selection module 505 may select the cache structure 215 forthe catalog 245 based at least in part on the catalog usage statistics.Usage status indicators may include historical usage (e.g. a totalnumber of searches), usage patterns (e.g. an increased number ofsearches at certain time periods), estimated future usage (e.g.extrapolated usage based on historical usage), and the like.

In one embodiment, the usage status indicators include an availabilityschedule. The selection module 505 may select the cache structure 215for the catalog 245 based at least in part on the availability schedule.The availability schedule may include one or more of scheduledavailability and scheduled unavailability for a catalog 245. A catalog245 may be unavailable when it is taken offline for maintenance such asa for a catalog reorganization. The availability schedule may alsoinclude one of scheduled availability and scheduled unavailability for ahost system 110 corresponding to a particular catalog 245. For example,if the particular catalog 245 is the master catalog 245 of a host system110 or otherwise specifically accessed by a host system, and that hostsystem 110 is scheduled for maintenance and will be unavailable for acertain period of time, the availability schedule may indicate suchunavailability.

The assignment policy may specify certain performance attributes,thresholds, and the like (generally or associated with particular ECScache structures 215), which, if satisfied by referenced usage statusindicators, may trigger an assignment to a particular ECS cachestructure 215 or a move from one ECS cache structure 215 to another. Forexample, the assignment policy may specify that if a catalog 245 has acertain number of errors, the volume record for the catalog 245 is to beisolated in its own ECS cache structure 245. The assignment policy mayspecify that certain volume records should be moved to different cachestructures 215 to balance I/O (e.g. a number of searches) among cachestructures 215. The data in the assignment policy may be comparedagainst catalog usage data residing in CAS statistics that is stored inCAS to determine which ECS cache structure 215 to select or whether areassignment is needed. In one embodiment, the assignment policy isstored in the CFRM policy.

The selection module 505 may additionally select an ECS cache structure215 for a catalog 245 based on one or more of current performanceactivity, historical catalog usage activity predicting future workloads,moving catalogs 245 with the highest usage requirements into the highestperforming ECS cache structures 215, and changing the overall number ofcatalog cache structures 215 so that the optimal number exists at anygiven time. For example, in one embodiment, the historical catalog usageactivity may indicate that a first catalog 245 sees an increase inactivity in the morning while another catalog 245 sees an increase inactivity in the afternoon. The selection module 505 may group thecatalogs 245 together in a common ECS cache structure 215 due to thedecreased likelihood that the catalogs 245 will be heavily used at thesame time.

In one embodiment, the selection module 505 may isolate a catalog 245 byassigning a catalog 245 to its own ECS cache structure 215 such that noother catalogs 245 are assigned to the cache structure. Specifically, inone embodiment, the cache structure 215 selected by the selection module505 is a temporary cache structure. The selection module 505 may movecatalog information for the catalog 245 from a first cache structure 215to the temporary cache structure 215 in response to one of scheduledunavailability for the catalog 245 and scheduled unavailability for ahost system 110 accessing the catalog 245. The selection module 505 maymove the catalog information from the temporary cache structure 215 tothe first cache structure 215 subsequent to the one of scheduledunavailability for the catalog 245 and scheduled unavailability for ahost system 110 accessing the catalog 245.

This temporary cache structure 215 may be a maintenance ECS cachestructure 215 set aside for temporary storage of volume records forcatalogs 245 undergoing maintenance or whose host systems 110 areundergoing maintenance, and the like. In a further embodiment, theselection module 505 isolates the catalog 245 in response to one ofdetermining that the catalog 245 is damaged, determining that a hostsystem 110 will be unavailable, and determining that the catalog 245will be unavailable. For example, if a particular host system 110 isscheduled to be taken off-line (e.g. one or more of disconnected fromthe coupling facility 105 and from other host systems 110), shut down,or otherwise made unavailable, leaving a volume record in the hostsystem's master catalog 245 in an ECS cache structure 215 with othervolume records may produce negative performance issues or interfere withthe other volume records. Therefore, the selection module 505 mayisolate the volume record for that host system 110 in its own ECS cachestructure 215. When the host system 110 is taken off-line, only the ECScache structure 215 for that host system 110 may be disconnected fromthe host systems 110.

The maintenance ECS cache structures 215 may be specified in theassignment policy. The selection module 505 may automatically selectcatalogs 245 to be assigned to these maintenance ECS cache structures215 when a particular catalog 245 is flagged as in need of maintenance.For example, during a catalog reorganization, a volume record of acatalog 245 may be set by the selection module 505 to be migrated to amaintenance ECS cache structure 215 automatically prior to the start ofthe reorganization with the target cache structure 215 being thestructure identified in the assignment policy as the maintenance cachestructure. After the reorganization finishes, the catalog 245 can beassigned back to its previous ECS cache structure 215 and its volumerecord copied back to its previous ECS cache structure 215.

As stated above, the assignment policy may specify that certain volumerecords should be moved to different cache structures 215 to balance I/O(e.g. a number of searches) among cache structures 215. Therefore, inone embodiment, the selection module 505 may assign high-use catalogs245 (e.g. catalogs 245 with use above a threshold) to ECS cachestructures 215 having no other catalogs 245 or catalogs 245 with loweruse in relation to other catalogs 245. Specifically, in certainembodiments, usage of a particular catalog 245 may meet a high usagethreshold meaning that the particular catalog 245 may have a number ofsearches meeting a threshold or meeting a certain threshold percentageof searches in comparison with other catalogs 245. The selection module505 may select a cache structure 215 for the particular catalog 245having one or more assigned catalogs 245 meeting a low usage thresholdmeaning that the assigned catalogs 245 may have a number of searchesmeeting a threshold or a certain percentage of searches meeting acertain threshold percentage of searches in comparison with othercatalogs 245.

The selection module 505 may select a cache structure 215 for a catalog245 for assignment and storage of the catalog's 245 volume record afterthe selection. The selection module 505 may also select a cachestructure 215 for a catalog 245 for assignment and storage of thecatalog's 245 volume record at a future point in time. For example, theselection module 505 may select a cache structure 215 and schedule atime (e.g. before the catalog 245 has maintenance performed) in whichthe catalog's 245 volume record will be copied to the cache structure.

In one embodiment, assigning a catalog 245 to a cache structure includesupdating a global ECS map of the coupling facility to inform the hostsystems 110 of the assignment.

The storage module 510, in one embodiment, stores catalog information ofthe catalog 245 in the cache structure 215 in response to the selectionmodule 505 selecting the cache structure and/or assigning the catalog245 to a cache structure 215. As stated above, the catalog informationmay include update information for the catalog 245 and the updateinformation may include a volume record (e.g. a VVR) for the catalog245.

The storage module 510 may store a volume record for a catalog 245 uponthe catalog 245 becoming active. The storage module 510 may also store avolume record for a catalog 245 previously assigned to a different ECScache structure 215. Specifically, in one embodiment, the storage module510 moves catalog information from a previous cache structure 215 toanother cache structure 215 according to the assignment policy. In theevent that the storage module 510 works with a catalog 245 that needs tobe migrated to a new cache, the catalog 245 is disconnected andreconnected to the new cache structure 215 and all cached data may bemoved by the storage module 510. By retaining cache data, performancemay remain the same since records do not need to be re-cached. In oneembodiment, the storage module 510 may trigger informational messages tothe console to announce the move. These messages may specify what cachestructure 215 the catalog 245 was moved from, what cache structure 215it is being moved to, a reason for the move, and the like.

The storage module 510 may copy a volume record uponassignment/selection by the selection module 505. In another embodiment,the storage module 510 may copy a volume record according to a schedule.For example, a volume record for a particular catalog 245 may bescheduled to be moved from one cache structure 215 to another prior tocatalog reorganization.

In one embodiment, the cache of the coupling facility 105 resides in asingle LPAR. Therefore, the storage module 510 may move volume recordsfrom cache structure 215 to cache structure 215 in the same LPAR.

FIG. 6 is a schematic block diagram illustrating another embodiment ofan assignment apparatus 220. The assignment apparatus 220 may be oneembodiment of the assignment apparatus 220 of FIG. 2. The assignmentapparatus 220 includes the identification module 500, the selectionmodule 505, and the storage module 510, wherein these modules may besubstantially similar to the like named modules described above inrelation to FIG. 5. In addition, the assignment apparatus 220 includes astructure management module 600, a statistics module 605, and a schedulemodule 610.

The structure management module 600, in one embodiment, activates anddeactivates ECS cache structures 215. Activating an ECS cache structure215 may include creating an ECS cache structure. Likewise, deactivatingan ECS cache structure 215 may include deleting an ECS cache structure.The structure management module 600 may one of activate and deactivateECS cache structures 215 based on one or more of the assignment policy,a number of active catalogs 245, and a grouping of catalogs 245 assignedto ECS cache structures 215 in the coupling facility 105. For example,the assignment policy may specify a maximum amount of ECS cachestructures 215 to be active at once, a minimum number of ECS cachestructures 215 to be active, and the like.

The statistics module 605, in one embodiment, obtains the catalog usagestatistics for a plurality of catalogs 245. In one embodiment, thestatistics module 605 obtains catalog usage statistics from catalogusage data provided by the Catalog Address Space (CAS). For example,statistics for total searches for each catalog 245 may be obtained fromthe catalog modify command: MODIFY CATALOG,REPORT,CACHE. The statisticsfrom CAS for a particular catalog 245 may be compared against thresholdsin the assignment policy and if the statistics meet the threshold, thecatalog 245 may be moved and/or initially assigned to a particular ECScache structure. The statistics module 605 may estimate future catalogusage based on the catalog usage statistics and the selection module 505may select cache structures 215 for catalogs 245 based on at least inpart on the future catalog usage. For example, if future catalog usageis predicted to increase for a particular catalog 245, the selectionmodule 505 may schedule the particular catalog 245 to be isolated ormoved to a cache structure 215 with lesser-searched catalogs 245 priorto the predicted increase.

The schedule module 610, in one embodiment, references availabilityschedules. The schedule module 610 may reference an availabilityschedule of one or more of a particular host system 110 and a particularcatalog 245. The availability schedule may include a maintenanceschedule specifying when a particular catalog 245 of host system 110will be undergoing maintenance.

FIG. 7 is a schematic flow chart diagram illustrating one embodiment ofa method 700 for assigning shared catalogs 245 to cache structures 215.The method 700 may be performed by a computer program product. Themethod 700 may perform at least a portion of the functions of theapparatus 220.

The method 700 starts and the identification module 700 identifies 705 acatalog 245 for sharing in association with a coupling facility 105. Thecoupling facility 105 includes a plurality of cache structures 215 forcatalogs 245 of a cluster computing system 100. The coupling facility105 is configured to facilitate data sharing among a plurality of hostsystems 110 of the cluster computing system. Next, the selection module505 selects 710 a cache structure 215 of the plurality of cachestructures 215 for the catalog 245 and/or assigns a cache structure 215to the catalog 245 according to an assignment policy. The assignmentpolicy is based on one or more usage status indicators. The storagemodule 510 stores 715 catalog information of the catalog 245 in thecache structure 215 and the method 700 ends.

FIG. 8 is a schematic flow chart diagram illustrating another embodimentof a method 800 for assigning shared catalogs 245 to cache structures215. The method 800 may be performed by a computer program product. Themethod 800 may perform at least a portion of the functions of theapparatus 350.

The method 800 starts and the identification module 500 selects 805 acatalog 245 for assignment evaluation. The catalog 245 may be an activecatalog 245 that is being accessed by one or more host systems 110 inthe cluster computing system 100, has a volume record stored in thecoupling facility 105, and the like. The schedule module 610 references810 an availability schedule of one or more of a host system 110specifically accessing the catalog 245, a host system 110 to which thecatalog 245 is the master catalog, and the catalog 245 itself.

If the schedule module 610 determines 815 that one or more of theseentities have scheduled unavailability, the storage module 510 copies830 the volume record from a first ECS cache structure 215 (e.g. the ECScache structure 215 in which the volume record resided upon initiationof the evaluation) to a second ECS cache structure 835. In oneembodiment, the storage module 510 isolates the volume record fromvolume records of other catalogs 245 so that other catalogs 245 may notbe affected when the catalog 245 or host system 110 becomes unavailable(e.g. when maintenance is performed). In one embodiment, the storagemodule 510 may copy the volume record substantially concurrently withthe evaluation. In one embodiment, the storage module 510 may schedulethe volume record to be copied prior to the time in which the hostsystem 110 or catalog 245 will become unavailable and the storage module510 then copies the volume record at that time.

If the identification module 500 identifies 840 more catalogs 245 toanalyze, the method 800 returns to step 805. If the identificationmodule 500 does not 840 identify more catalogs 245 to analyze, themethod 800 ends.

Alternatively, returning to decision 815, if the schedule module 610does not detect 815 scheduled unavailability, the statistics module 605references 820 catalog usage statistics for one or more of the catalog245 and one or more additional catalogs 245. If the statistics module605 determines 815 that one or more of the catalog 245 and one or moreadditional catalogs 245 meet various usage thresholds according to theassignment policy, the storage module 510 copies 830 the volume recordfrom a first ECS cache structure 215 (e.g. the ECS cache structure 215in which the volume record resided upon initiation of the evaluation) toa second ECS cache structure 835. For example, if the catalog 245 meetsa high usage threshold and one or more catalogs 245 in the second ECScache structure 215 meet low usage thresholds, the storage module 510may copy the volume record from the first ECS cache structure 215 to thesecond ECS cache structure. If the identification module 500 identifies840 more catalogs 245 to analyze, the method 800 returns to step 805. Ifthe identification module 500 does not identify 840 more catalogs 245 toanalyze, the method 800 ends.

The embodiments may be practiced in other specific forms. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. An apparatus comprising: one or more memoryexecuted by a processor; a coupling facility comprising a plurality ofcache structures for catalogs of a cluster computing system, thecoupling facility configured to facilitate data sharing among aplurality of host systems of the cluster computing system; a statisticsmodule configured to obtain one or more usage status indicators forcatalogs for estimating future catalog usage, wherein the usage statusindicators comprise historical usage, usage patterns, and estimatedfuture usage; an identification module configured to identify a catalogassigned to a first cache structure of the plurality of cache structuresfor sharing in association with the coupling facility in response to theone or more usage status indicators for the catalog meeting a threshold;a selection module configured to select a second cache structure of theplurality of cache structures for the catalog based on the one or moreusage status indicators for the catalog according to an assignmentpolicy, wherein the assignment policy comprises assigning the catalog tothe second cache structure, the second cache structure having nocatalogs or other catalogs with usage status indicators that do not meetthe threshold; and assigning a heavily used catalog its own ECS(Enhanced Sharing Catalog) cache structure such that no other catalogsare assigned to this cache structure; and a storage module configured tostore catalog information of the catalog in the second cache structurein response to the selection module selecting the second cachestructure, wherein storing catalog information of the catalog in thesecond cache structure comprises copying a volume record of the catalogto the second cache structure.
 2. The apparatus of claim 1, wherein thecatalog information comprises update information for the catalog,wherein the update information comprises an integrity Virtual StorageAccess Method (VSAM) volume record (VVR) for the catalog.
 3. Theapparatus of claim 1, further comprising an structure management moduleconfigured to one of activate and deactivate one or more of theplurality of cache structures based on one or more of the assignmentpolicy, a number of active catalogs, and a grouping of catalogs assignedto cache structures in the coupling facility.
 4. The apparatus of claim1, wherein the usage status indicators further comprise an availabilityschedule and wherein the apparatus further comprises a schedule moduleconfigured to reference an availability schedule of one or more of aparticular host system and a particular catalog, wherein the selectionmodule is configured to select the second cache structure for thecatalog based at least in part on the availability schedule.
 5. Theapparatus of claim 1, wherein the selection module is further configuredto isolate the catalog to the second cache structure, wherein no othercatalogs are assigned to the second cache structure beside the catalog.6. The apparatus of claim 5, wherein the selection module isolates thecatalog in response to one of determining that the catalog is damaged,determining that a host system will be unavailable, and determining thatthe catalog will be unavailable.
 7. A method for assigning a cachestructure to a catalog, the method comprising: obtaining one or moreusage status indicators for catalogs for estimating future catalogusage, wherein the usage status indicators comprise historical usage,usage patterns, and estimated future usage; identifying a catalog forsharing in association with a coupling facility, the coupling facilitycomprising a plurality of cache structures for catalogs of a clustercomputing system, the coupling facility configured to facilitate datasharing among a plurality of host systems of the cluster computingsystem, wherein identifying a catalog comprises selecting a catalogassigned to a first cache structure of the plurality of cache structuresin response to one or more usage status indicators for the catalogmeeting a threshold; assigning the catalog to a second cache structureof the plurality of cache structures based on the one or more usagestatus indicators according to an assignment policy, wherein theassignment policy comprises assigning the catalog to the second cachestructure, the second cache structure having no catalogs or othercatalogs with usage status indicators that do not meet the threshold;and assigning a heavily used catalog its own ECS (Enhanced SharingCatalog) cache structure such that no other catalogs are assigned tothis cache structure; and storing catalog information of the catalog inthe second cache structure in response to selecting the second cachestructure, wherein storing catalog information of the catalog in thesecond cache structure comprises copying a volume record of the catalogto the second cache structure.
 8. The method of claim 7, wherein thecatalog information comprises update information for the catalog andwherein the update information comprises an integrity Virtual StorageAccess Method (VSAM) volume record (VVR) for the catalog.
 9. The methodof claim 7, wherein the usage status indicators of the other catalogswith usage status indicators that do not meet the threshold remain belowa second threshold, the second threshold being lower than the threshold.10. The method of claim 7, wherein the second cache structure comprisesa temporary cache structure and wherein the method further comprisesmoving catalog information for the catalog from the first cachestructure to the temporary cache structure in response to one ofscheduled unavailability for the catalog and scheduled unavailabilityfor a host system accessing the catalog, wherein moving the cataloginformation from the temporary cache structure to the first cachestructure occurs subsequent to the one of scheduled unavailability forthe catalog and scheduled unavailability for a host system accessing thecatalog.
 11. The method of claim 7, wherein the usage status indicatorsfurther comprise an availability schedule and wherein the method furthercomprises referencing an availability schedule of one or more of aparticular host system and a particular catalog, wherein the secondcache structure for the catalog is selected based at least in part onthe availability schedule.
 12. A computer program product for assigninga cache structure to a catalog, the computer program product comprisinga computer readable storage medium storing machine readable codeexecuted by a processor to perform the operations of: obtaining one ormore usage status indicators for catalogs, for estimating future catalogusage, wherein the usage status indicators comprise historical usage,usage patterns, and estimated future usage; identifying a catalog forsharing in association with a coupling facility according to EnhancedCatalog Sharing (ECS), the coupling facility comprising a plurality ofcache structures for catalogs of a cluster computing system, thecoupling facility configured to facilitate data sharing among aplurality of host systems of the cluster computing system, whereinidentifying a catalog comprises selecting a catalog assigned to a firstcache structure of the plurality of cache structures in response to oneor more usage status indicators for the catalog meeting a threshold;assigning the catalog to a second cache structure of the plurality ofcache structures based on one or more of an availability indicator andthe one or more usage status indicators for the catalog according to anassignment policy stored in a coupling facility resource management(CFRM) data set of the cluster computing system, wherein the assignmentpolicy comprises assigning the catalog to the second cache structure,the second cache structure having no catalogs or other catalogs withusage status indicators that do not meet the threshold; and assigning aheavily used catalog its own ECS (Enhanced Sharing Catalog) cachestructure such that no other catalogs are assigned to this cachestructure; and storing a Virtual Storage Access Method (VSAM) volumerecord (VVR) corresponding to the catalog in the second cache structurein response to selecting the second cache structure, the VVR comprisingupdate information.
 13. The computer program product of claim 12,further comprising isolating the catalog to the second cache structure,wherein no other catalogs are assigned to the second cache structurebeside the catalog.
 14. The computer program product of claim 13,wherein the catalog is isolated in response to one of determining thatthe catalog is damaged, determining that a host system will beunavailable, and determining that the catalog will be unavailable.